Different combinations of these bases are what provide the instructions for every function in the human body.
In beta-thalassemia, the disease is caused by a mistake in a single base in the genetic code – known as a point mutation. The Chinese team showed it was possible to find the point mutation and change a ‘G’ to an ‘A.’, fixing the problem.
Junjiu Huang, one of the researchers, told the BBC News website: “We are the first to demonstrate the feasibility of curing genetic disease in human embryos by base editor system.”
The technique, known as base editing, was pioneered by Prof David Liu of Harvard University, who claims it has fewer side-effects than Crispr.
He told the BBC: “About two-thirds of known human genetic variants associated with disease are point mutations.
“So base editing has the potential to directly correct, or reproduce for research purposes, many pathogenic [mutations].”
The research group at Sun Yat-sen University in Guangzhou was the first group in the world to use Crisp on human embryos, a breakthrough which shocked some scientists and led to claims that China was acting like ‘The Wild West’ of science.
Prof Robin Lovell-Badge, from the Francis Crick Institute in London, said the ethics of such procedures were still up for debate, and are unlikely to be available in the near future.
“There would need to be far more debate, covering the ethics, and how these approaches should be regulated,” he said.
“And in many countries, including China, there needs to be more robust mechanisms established for regulation, oversight, and long-term follow-up.
“It is a complex paper, with some interesting results that might indicate a route to avoiding certain genetic diseases in both somatic and germline treatments – although it is far too early to even consider applying the methods clinically.”
Dr Helen Claire O’Neill, Programme Director, Reproductive Science and Women’s Health, University College London, said: “Many hereditary diseases, such as β-thalassemia, have life-threatening implications and yet are the result of a mutation which causes a single letter change in an individual’s genome.
“The work presented here uses a technique called “base editing” which attempts to repair a mutation at the single letter (or base), resulting in the hopeful correction of the mutation. It does this without the need for breaking the double-stranded DNA.
“More work is needed to assess the precision of this base editing technology (and) to fully investigate both efficiency and specificity of the technique.”
The Chinese research is published in the journal Protein and Cell.